PHYS20008 Lecture Notes - Lecture 11: Biceps, Homeostasis, Myosin
10 May 2018
School
Department
Course
Professor
Lecture 11
- Fatigue does not result from a loss of available ATP: myosin head is bound to actin
filament until ATP comes in and enables myosin head to release from actin filament,
stage of myosin locked onto actin is very brief because lots of ATP in body, ATP
stores break down when we die (rigor mortis, muscles cross linked, myosin heads
unable to release from actin filament until all the proteins degrade and stiffness
wears out)
- Cause of fatigue: unknown
find more resources at oneclass.com
find more resources at oneclass.com
-
- Muscle fibres → myofibrils → sarcomeres, organised between various lines and discs
- Each individual sarcomere → thick filaments (myosin) overlapping thin filaments
(actin), crossbridge cycle occurs to ratchet filaments closer together and shorten
them
find more resources at oneclass.com
find more resources at oneclass.com
- Crossbridge cycle: ATP binding, hydrolysed → energy of head to cock itself into place
→ tight bond with actin filament and myosin head, when calcium has pulled
tropomyosin molecule away → causes inorganic phosphate to kick off myosin head
and pulls trigger to crossbridge cycle
- Three types of contraction: isometric, isotonic, and eccentric
-
- Isometric contraction: iso = the same, metric = length; contracting muscle/exerting
force but length isn’t changing, muscle cannot overcome load it’s trying to move, will
build muscle, e.g. yoga; force pulling muscles in one direction, crossbridge pulling
back in other direction → balance; build force but muscle length doesn’t change
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Muscle fibres myofibrils sarcomeres, organised between various lines and discs. Each individual sarcomere thick filaments (myosin) overlapping thin filaments (actin), crossbridge cycle occurs to ratchet filaments closer together and shorten them. Crossbridge cycle: atp binding, hydrolysed energy of head to cock itself into place. Tight bond with actin filament and myosin head, when calcium has pulled tropomyosin molecule away causes inorganic phosphate to kick off myosin head and pulls trigger to crossbridge cycle. Three types of contraction: isometric, isotonic, and eccentric. To lift load: we first need to develop enough force in muscle to overcome weight of load once overcome weight of load, we move it no longer need additional force, muscle shortens. X axis: force over maximum isometric force (maximum velocity = 0 cause nothing is shortening) Y axis: contractile velocity, how quickly muscle is contracting. Force needed to exert is higher velocity to lift it/shorten muscle is lower.
